Including cc-0 when cc-by is searched seems like a good idea.

Some licenses implicitly imply that you release it on other licenses as well.

From a legal standpoint, this is probably incorrect. CC0 and CC-BY for example prohibit re-licensing the original. I agree however, that the search is problematic for people who don't know about the license details.

A little feedback (when choosing the license). Click CC-0 and CC-BY is selected as well. (But only CC-0 is saved)

I don't understand that one.

Secondly, a small help page on license could be helpfull to some people.

Absolutely! One example for this is freesound.org/help/faq/#licenses. We seem to already have a section that has such a function: "I'm a commercial (closed-source) game developer. Can I use this art?" on opengameart.org/content/faq. We can add a "?" link to it from the license form widget.

The feedback I think would be better handled with a popup say that a license is redundant.

The searching I very much agree with, though perhaps have an "include compatible licenses" option that defaults to on as people might still want to find something with a specific license.

I allways imagined that this might be the case with searching (though have always been too lazy to test it) so license my stuff both as GPL2+ and GPL3+ even though I feel kind of stupid doing so.

CC0 can be relicensed as you see fit. From the text of CC-By it seems it can be relicensed as well (at least a derivative work does not need to have the same license). I am not a lawyer though.

I am pretty sure CC-0 prohibits nothing.  Hence the 0.

I have my doubts that you may take Charles_Stewart_Parnell,_portrait_1885 or 16x16-dungeon-tiles and redistribute them without modifications under CC-BY or CC-BY-SA.

@qubodup: This means that cc-by-sa licensed game assets cannot contain cc-by or cc-0 because cc-by-sa would force other assets to be cc-by-sa as well. There should be license compatibility list or something. There are some lists for software, but as I am not an artist I do not know resources for this domain.

@cemkalyoncu it is correct that a game that accepts cc-by-sa 3 but not cc-by 3, would not be able to use cc-by 3 art without changing it. This is because 4. a. prohibits sublicensing of the original work.

The inability to re-license unchanged cc-by 3 art is a good thing (legally) in my eyes, because it (legally) prevents people from spreading cc-by 3 art, claiming that it is cc-by-nc-nd art.

When I create work under cc-by 3, I would be fine with the original being distributed in original form under cc-by-sa 3, however I would be offended, if it was distributed in original form under cc-by-nc or cc-by-nd (because I dispise these licenses).

(I am not sure that CC0 prohibits re-licensing the original work but I would be surprised.)

Public domain means public domain.  There are no restrictions on what you do, with the possible exception of the author's moral rights.  That's why it's considered essentially synonymous with WTFPL.  Of course, if you're distributing it under CC-By-SA, it has a lot less sticking power because it is, of course, a dual license essentially and need not be followed.  But there is nothign preventing you from doing it.

@qubodup: I read the entire conduct, so it is not simply attribution required. So I would kindly ask a BSD style license to be included in the website. BSD style licenses requires only the license text, which is pretty simple to be left intact. You can chance the license as long as the given copyright notice and license info is not altered. This applies to MIT/BSD/Apache (current)/Zlib licenses. You can use material licensed with these licenses and include them in a library which uses a completely different license.

Definitions of the boundaries of the public domain in relation to copyright, or intellectual property more generally, regard the public domain as a negative space, that is, it consists of works that are no longer in copyright term or were never protected by copyright law.

- en.wikipedia.org/wiki/Public_domain#Definition

My thinking is: if a work is not protected by copyright, a license cannot be applied to it, as it depends on copyright.

@cemkalyoncu: long ago, we had one, two or three of the MIT/BSD/zLib licenses on OGA but they were removed, I assume because they were only used by two users at best. LGPL options also disappeared.

It would be not worth adding the MIT or BSD license, just to have one single user use it and then another coming along, asking for zlib licensing as an option.

If there was a permissive license that was specifically worded for all works of art, not only software, and it would have been approved by Debian, Definition of Free Cultural Works and ideally FSF, I would gladly discuss including it on OGA.

I am not a lawyer, I will not spend time writing or reviewing licenses.

I recommend you use CC0 or use CC-BY 3 and include the license you desire manually as a tag (and in the description text or as an attachement .txt).

Note: I am not an admin of OGA, I am merely a moderator and have a big mouth. ;)

Its important to know that CC0 is not same as public domain. PD is an automatic state, which is applied after IP rights are expired. CC0 is called public domain dedication, if applicable it states the author releases all copyrights. This binds the author, not the user. However, this is not valid in Europe, so the license which binds the user, allows the work to be used without any restrictions. In any case author non-revokably promises not to exercise his copyrights.

@qubodup: actually you are right, its not to hard to explicitly allow relicensing as long as the credits remains intact.